The present invention relates to the testing of high voltage cable installations and, more particularly, to an apparatus and method for providing a high voltage to be injected into a cable installation to permit identification of incipient faults.
Electrical power equipment and systems should be tested on-site prior to their initial energization and periodically during their service life to ensure that defective components leading to service failures are identified and repaired. Although this is true for all types of high voltage power equipment, this is particularly important for power cables.
In testing a cable, a voltage equivalent to several times its normal rated value is impressed upon its insulation for a predetermined time duration to determine one or more of the following:
(a) whether the cable survives the test without failure PA1 b) the leakage current as a function of time and the voltage applied PA1 c) the dissipation factor of the cable insulation PA1 d) the existence, and location of any partial discharge (PD) PA1 e) any other characteristic relevant to the cable operation
The best method for testing the cable utilizes an alternating voltage (AC) at the intended power frequency (50 or 60 Hz) because this corresponds to the real service condition. If a long cable (several thousand feet in length) intended for a 15 Kv system or higher is to be tested at an AC voltage equivalent to three times its service voltage level, a very bulky, heavy and expensive test transformer would be required, generally weighing in excess of 3,000 pounds and costing over $50,000.
In an effort to provide an alternative approach, several different field testing strategies have been adopted in the past.